Methods and systems for co2 condensation

ABSTRACT

In accordance with one aspect of the present invention, methods of condensing carbon dioxide (CO 2 ) from a CO 2  stream are provided. The method includes (i) compressing and cooling the CO 2  stream to form a partially cooled CO 2  stream, wherein the partially cooled CO 2  stream is cooled to a first temperature. The method includes (ii) cooling the partially cooled CO 2  stream to a second temperature by magneto-caloric cooling to form a cooled CO 2  stream. The method further includes (iii) condensing at least a portion of CO 2  in the cooled CO 2  stream to form a condensed CO 2  stream. Systems for condensing carbon dioxide (CO 2 ) from a CO 2  stream are also provided

BACKGROUND

1. Technical Field

The present disclosure relates to methods and systems for carbon dioxide(CO₂) condensation using magneto-caloric cooling. More particularly, thepresent disclosure relates to methods and systems for CO₂ condensationin an intercooled compression and pumping train using magneto-caloriccooling.

2. Discussion of Related Art

Power generating processes that are based on combustion of carboncontaining fuel typically produce CO₂ as a byproduct. It may bedesirable to capture or otherwise separate the CO₂ from the gas mixtureto prevent the release of CO₂ into the environment and/or to utilize CO₂in the power generation process or in other processes. It may be furtherdesirable to liquefy/condense the separated CO₂ to facilitate transportand storage of the separated CO₂. CO₂ compression, liquefaction andpumping trains may be used to liquefy CO₂ for desired end-useapplications. However, methods for condensation/liquefaction of CO₂ maybe energy intensive.

Thus, there is a need for efficient methods and systems for condensationof CO₂. Further, there is a need for efficient methods and systems forcondensation of CO₂ in intercooled compression and pumping trains.

BRIEF DESCRIPTION

In accordance with one aspect of the present invention, a method ofcondensing carbon dioxide (CO₂) from a CO₂ stream is provided. Themethod includes (i) compressing and cooling the CO₂ stream to form apartially cooled CO₂ stream, wherein the partially cooled CO₂ stream iscooled to a first temperature. The method includes (ii) cooling thepartially cooled CO₂ stream to a second temperature by magneto-caloriccooling to form a cooled CO₂ stream. The method further includes (iii)condensing at least a portion of CO₂ in the cooled CO₂ stream at thesecond temperature to form a condensed CO₂ stream.

In accordance with another aspect of the present invention a method ofcondensing carbon dioxide (CO₂) from a CO₂ stream is provided. Themethod includes (i) cooling the CO₂ stream in a first cooling stagecomprising a first heat exchanger to form a first partially cooled CO₂stream. The method further includes (ii) compressing the first partiallycooled CO₂ stream to form a first compressed CO₂ stream. The methodfurther includes (iii) cooling the first compressed CO₂ stream in asecond cooling stage comprising a second heat exchanger to form a secondpartially cooled CO₂ stream. The method further includes (iv)compressing the second partially cooled CO₂ stream to form a secondcompressed CO₂ stream. The method further includes (v) cooling thesecond compressed CO₂ stream to a first temperature in a third coolingstage comprising a third heat exchanger to form a partially cooled CO₂stream. The method further includes (vi) cooling the partially cooledCO₂ stream to a second temperature by magneto-caloric cooling to form acooled CO₂ stream. The method further includes (vii) condensing at leasta portion of CO₂ in the cooled CO₂ stream at the second temperature toform a condensed CO₂ stream.

In accordance with yet another aspect of the present invention, a systemfor condensing carbon dioxide (CO₂) from a CO₂ stream is provided. Thesystem includes (i) one or more compression stages configured to receivethe CO₂ stream. The system further includes (ii) one or more coolingstages in fluid communication with the one or more compression stages,wherein a combination of the one or more compression stages and the oneor more cooling stages is configured to compress and cool the CO₂ streamto a first temperature to form a partially-cooled CO₂ stream. The systemfurther includes (iii) a magneto-caloric cooling stage configured toreceive the partially-cooled CO₂ stream and cool the partially-cooledCO₂ stream to a second temperature to form a cooled CO₂ stream. Thesystem further includes (iv) a condensation stage configured to condensea portion of CO₂ in the cooled CO₂ stream at the second temperature,thereby condensing CO₂ from the cooled compressed CO₂ stream to form acondensed CO₂ stream.

Other embodiments, aspects, features, and advantages of the inventionwill become apparent to those of ordinary skill in the art from thefollowing detailed description, the accompanying drawings, and theappended claims.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a flow chart for a method of CO₂ condensation from a CO₂stream, in accordance with one embodiment of the invention.

FIG. 2 is a flow chart for a method of CO₂ condensation from a CO₂stream, in accordance with one embodiment of the invention.

FIG. 3 is a block diagram of a system for CO₂ condensation from a CO₂stream, in accordance with one embodiment of the invention.

FIG. 4 is a block diagram of a system for CO₂ condensation from a CO₂stream, in accordance with one embodiment of the invention.

FIG. 5 is a block diagram of a system for CO₂ condensation from a CO₂stream, in accordance with one embodiment of the invention.

FIG. 6 is a block diagram of a system for CO₂ condensation from a CO₂stream, in accordance with one embodiment of the invention.

FIG. 7 is a block diagram of a system for CO₂ condensation from a CO₂stream, in accordance with one embodiment of the invention.

FIG. 8 is a block diagram of a system for CO₂ condensation from a CO₂stream, in accordance with one embodiment of the invention.

FIG. 9 is a block diagram of a system for CO₂ condensation from a CO₂stream, in accordance with one embodiment of the invention.

FIG. 10 is a pressure versus temperature diagram for CO₂.

DETAILED DESCRIPTION

As discussed in detail below, embodiments of the present inventioninclude methods and systems suitable for CO₂ condensation. As notedearlier, liquefying and pumping of CO₂ may require high energy input.For example, a pressure of approximately 60 bar may be required toliquefy CO₂ at 20° C. In some embodiments, an intermediate magneticcooling step advantageously lowers the CO₂ temperature to less than 0°C., significantly reducing the required work of the overall system. Insome embodiments, depending on the coefficient of performance of themagneto-caloric cooling system, an overall efficiency improvement ofabout 10 percent to about 15 percent may be possible using the methodsand systems described herein.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about”, is not limited to the precise valuespecified. In some instances, the approximating language may correspondto the precision of an instrument for measuring the value.

In the following specification and the claims, the singular forms “a”,“an” and “the” include plural referents unless the context clearlydictates otherwise.

In one embodiment, as shown in FIGS. 1 and 3, a method 10 for condensingcarbon dioxide from a CO₂ stream is provided. The term “CO₂ stream”, asused herein, refers to a stream of CO₂ gas mixture emitted as a resultof the processing of fuels, such as, natural gas, biomass, gasoline,diesel fuel, coal, oil shale, fuel oil, tar sands, and combinationsthereof. In some embodiments, the CO₂ stream includes a CO₂ streamemitted from a gas turbine. In particular embodiments, the CO₂ streamincludes a CO₂ gas mixture emitted from a coal or natural gas-firedpower plant.

In some embodiments, the CO₂ stream further includes one more ofnitrogen, nitrogen dioxide, oxygen, or water vapor. In some embodiments,the CO₂ stream further includes impurities or pollutants, examples ofwhich include, but are not limited to, nitrogen, nitrogen oxides, sulfuroxides, carbon monoxide, hydrogen sulfide, unburnt hydrocarbons,particulate matter, and combinations thereof. In particular embodiments,the CO₂ stream is substantially free of the impurities or pollutants. Inparticular embodiments, the CO₂ stream essentially includes carbondioxide.

In some embodiments, the amount of impurities or pollutants in the CO₂stream is less than about 50 mole percent. In some embodiments, theamount of impurities or pollutants in the CO₂ stream is less than about20 mole percent. In some embodiments, the amount of impurities orpollutants in the CO₂ stream is in a range from about 10 mole percent toabout 20 mole percent. In some embodiments, the amount of impurities orpollutants in the CO₂ stream is less than about 5 mole percent.

In one embodiment, the method includes receiving a CO₂ stream 101, asindicated in FIG. 3, from a hydrocarbon processing, combustion,gasification or a similar power plant (not shown). As indicated in FIGS.1 and 3, at step 11, the method 10 includes compressing and cooling theCO₂ stream 101 to form a partially cooled CO₂ stream 201. In someembodiments, the CO₂ stream 101 may be compressed using or morecompression stages 120. In some embodiments, the CO₂ stream may becooled using or more cooling stages 110.

In some embodiments, the CO₂ stream 101 may be compressed to a desiredpressure by using one or more compression stages, as indicated by 120 inFIG. 3. As indicated in FIG. 3, the compression stage 120 may furtherinclude one or more compressors, such as, 121 and 122, in someembodiments. It should be noted that in FIG. 3, the two compressors 121and 122 are shown as an exemplary embodiment only and the actual numberof compressors and their individual configuration may vary depending onthe end result desired. In one embodiment, the CO₂ stream 101 may becompressed to a pressure and temperature desired for the magneticcooling and condensation steps 12 and 13, respectively. In someembodiments, the CO₂ stream 101 may be compressed to a pressure in arange from about 10 bar to about 60 bar prior to the magnetic coolingstep 12. In particular embodiments, the CO₂ stream 101 may be compressedto a pressure in a range from about 20 bar to about 40 bar prior to themagnetic cooling step 12.

In some embodiments, the CO₂ stream 101 may be cooled to a desiredtemperature by using one or more cooling stages, as indicated by 110 inFIG. 3. As indicated in FIG. 3, the cooling stage 110 may furtherinclude one or more heat exchangers, such as, 111, 112 and 113, in someembodiments. It should be noted that in FIG. 3, the three heatexchangers 111, 112, and 113 are shown as an exemplary embodiment onlyand the actual number of heat exchangers and their individualconfiguration may vary depending on the end result desired. In someembodiments, one or more of the heat exchangers may be cooled using acooling medium. In some embodiments, one more of the heat exchangers maybe cooled using cooling air, cooling water, or both, as indicated by 115in FIG. 3. In some embodiments, the cooling stage may further includeone or more intercoolers to cool the exhaust gas stream 101 withoutaffecting the pressure.

It should be further noted that in FIG. 3, the configuration of coolingstage 110 and compression stage 120 is shown as an exemplary embodimentonly and the actual configuration may vary depending on the end resultdesired. For example, in some other embodiments, the method may includecooling the CO₂ stream in a heat exchanger 111 prior to compressing theCO₂ stream in a compressor 121 (not shown).

In some embodiments, the method further includes cooling the CO₂ stream101 to a first temperature by expanding the CO₂ stream in one or moreexpanders 123, as indicated in FIG. 8. In some embodiments the methodincludes an expansion step that decreases the pressure of the CO₂ stream101 from absolute pressure levels greater than about 20 bar to pressurelevels of around 20 bar, thereby decreasing the temperature of the CO₂stream 101 to values lower than that may be reached by air or watercooling. Without being bound any theory, it is believed that byemploying the expansion step, the overall duty of the magneto-caloriccooling step 12 may be reduced, as the inlet temperature of thepartially-cooled CO₂ stream to the magneto-caloric step may be lowerthan that without an expansion step. In some embodiments, the workextracted in the expansion step may be further used for themagneto-caloric cooling step 12.

In one embodiment, the CO₂ stream 101 may be cooled to a temperature andpressure desired for the magnetic cooling and condensation steps 12 and13. In one embodiment, the method includes compressing and cooling theCO₂ stream 101 to form a partially cooled CO₂ stream 201, as indicatedin FIG. 3. In one embodiment, the method further includes cooling theCO₂ stream 101 to a first temperature by expanding the CO₂ stream in oneor more expanders 123 to form the partially cooled CO₂ stream 201, asindicated in FIG. 8.

In one embodiment, the method includes cooling the partially cooled CO₂stream 201 to a first temperature. In some embodiments, the partiallycooled CO₂ stream 201 may be cooled to a temperature in a range fromabout 5 degrees Celsius to about 35 degrees Celsius, prior to themagnetic cooling step 12. In particular embodiments, the partiallycooled CO₂ stream 201 may be cooled to a temperature in a range fromabout 10 degrees Celsius to about 25 degrees Celsius, prior to themagnetic cooling step 12.

As noted earlier, in the absence of an additional magnetic cooling step,CO₂ in the partially cooled CO₂ stream 201 is typically liquefied at atemperature in a range from about 20 degrees Celsius to about 25 degreesCelsius. The condensation temperature is determined by the temperatureof the cooling medium, which can be cooling water or air. As shown inFIG. 10, at a condensation temperature in a range from about 20 degreesCelsius to about 25 degrees Celsius, an absolute pressure ofapproximately 60 bar is required to liquefy CO₂. In contrast, by coolingthe CO₂ stream to a temperature in a range from about −25 degreesCelsius to about 0 degrees Celsius, lower pressure may be advantageouslyused for condensing CO₂ from the partially cooled CO₂ stream 201.

In one embodiment, the method further includes, at step 12, cooling thepartially cooled CO₂ stream 201 to a second temperature bymagneto-caloric cooling to form a cooled CO₂ stream 302, as indicated inFIGS. 1 and 3. In one embodiment, the method includes cooling thepartially-cooled CO₂ stream 201 using a magneto-caloric cooling stage200, as indicated in FIG. 3.

In some embodiments, a magneto-caloric cooling stage 200 includes a heatexchanger 212 and an external magneto-caloric cooling device 211. Insome embodiments, the magneto-caloric cooling device 211 is configuredto provide cooling to the heat exchanger 212, as shown in FIG. 3.

In one embodiment, the magneto-caloric cooling device 211 includes acold and a hot heat exchanger, a permanent magnet assembly or aninduction coil magnet assembly, a regenerator of magneto-caloricmaterial, and a heat transfer fluid cycle. In one embodiment, the heattransfer fluid is pumped through the regenerator and the heat exchangerby a fluid pump (not shown).

In one embodiment, the magneto-caloric cooling devices works on anactive magnetic regeneration cycle (AMR) and provides cooling power to aheat transfer fluid by sequential magnetization and demagnetization ofthe magneto-caloric regenerator with flow reversal heat transfer flow.In some embodiments, the sequential magnetization and demagnetization ofthe magneto-caloric regenerator may be provided for by a rotary set-upwhere the regenerator passes through a bore of the magnet system. Insome other embodiments, the sequential magnetization and demagnetizationof the magneto-caloric regenerator may be provided for by areciprocating linear device. An exemplary magnet assembly andmagneto-caloric cooling device are described in U.S. patent applicationSer. No. 12/392,115, filed on Feb. 25, 2009, and incorporated herein byreference in its entirety for any and all purposes, so long as notdirectly contradictory with the teachings herein.

In some embodiments, the heat at the hot heat exchanger may be deliveredto the ambient environment. In some other embodiments, the heat at thehot heat exchanger may be delivered to the return flow of the condensedand liquefied CO₂ after the pumping of the liquid CO₂, as describedherein later.

As noted earlier, the magneto-caloric cooling stage further includes aheat exchanger 212, wherein the magneto-caloric cooling device 211 isconfigured to provide cooling to the heat exchanger 212. In oneembodiment, the heat exchanger 212 is in fluid communication with theone or more cooling stages 110 and the one or more compression stages120. In one embodiment, the heat exchanger 212 is in fluid communicationwith the partially cooled CO₂ stream 201 generated after the compressionand cooling step 11.

In some embodiments, the magneto-caloric cooling device 211 isconfigured to provide cooling to the heat exchanger 212 such that thepartially cooled CO₂ stream 201 is cooled to the second temperature. Inone embodiment, the second temperature is in a range of from about 0degrees Celsius to about −25 degrees Celsius.

In one embodiment, the second temperature is in a range of from about 5degrees Celsius to about −20 degrees Celsius. As noted earlier, the step13 of cooling the partially-cooled CO₂ stream in the magneto-caloriccooling stage results in a cooled CO₂ stream.

In some embodiments, the magneto-caloric cooling device 211 isconfigured to provide cooling to the heat exchanger 212 such that thepartially cooled CO₂ stream 201 is cooled to the second temperature,such that CO₂ condenses from the cooled CO₂ stream. As noted earlier,the method includes compressing the CO₂ stream 101 to a pressure in arange from about 20 bar to about 40 bar, in some embodiments. Asindicated in FIG. 10, at a pressure level of 40 bar, the CO₂ condensesat a temperature of 5 C. Further, as indicated in FIG. 10, at a pressurelevel of 20 bar, the CO₂ condenses at a temperature of −20 C.

In one embodiment, the method further includes, at step 13, condensingat least a portion of CO₂ in the cooled CO₂ stream at the secondtemperature, thereby condensing CO₂ from the cooled CO₂ stream to form acondensed CO₂ stream 302. In one embodiment, the method includescondensing at least a portion of CO₂ in the cooled CO₂ stream at apressure in a range of from about 20 bar to about 60 bar. In oneembodiment, the method includes condensing at least a portion of CO₂ inthe cooled CO₂ stream at a pressure in a range of from about 20 bar toabout 40 bar. Accordingly, the method of the present inventionadvantageously allows for condensation of CO₂ at a lower pressure, insome embodiments.

In some embodiments, the method includes performing the steps of coolingthe partially cooled CO₂ stream to form a cooled CO₂ stream 12 andcondensing CO₂ from the cooled CO₂ stream 13 simultaneously. In someother embodiments, the method includes performing the steps of coolingthe partially cooled CO₂ stream to form a cooled CO₂ stream 12 andcondensing CO₂ from the cooled CO₂ stream 13 sequentially.

As indicated in FIG. 3, in some embodiments, a cooled CO₂ stream may begenerated from the partially cooled CO₂ stream 201 in the heat exchanger212. In such embodiments, a portion of CO₂ from the cooled CO₂ streamcondenses in the heat-generator itself forming a condensed CO₂ stream302, as indicated in FIG. 3.

In some other embodiments, as indicated in FIG. 4, a cooled CO₂ stream301 is generated from the partially cooled CO₂ stream 201 in the heatexchanger 212. The method further includes transferring the cooled CO₂stream 301 to a condenser 213, as indicated in FIG. 4. In suchembodiments, a portion of CO₂ from the cooled CO₂ stream 301 condensesin the condenser 213 and forms a condensed CO₂ stream 302, as indicatedin FIG. 4.

In some embodiments, the method includes condensing at least about 95weight percent of CO₂ in the CO₂ stream 101 to form the condensed CO₂stream 302. In some embodiments, the method includes condensing at leastabout 90 weight percent of CO₂ in the CO₂ stream 101 to form thecondensed CO₂ stream 302. In some embodiments, the method includescondensing 50 weight percent to about 90 weight percent of CO₂ in theCO₂ stream 101 to form the condensed CO₂ stream 302. In someembodiments, the method includes condensing at least about 99 weightpercent of CO₂ in the CO₂ stream 101 to form the condensed CO₂ stream302.

In some embodiments, as noted earlier, the CO₂ stream 101 furtherincludes one or more components in addition to carbon dioxide. In someembodiments, the method further optionally includes generating a leanstream (indicated by dotted arrow 202) after the steps ofmagneto-caloric cooling (step 12) and CO₂ condensation (step 13). Theterm “lean stream” 202 refers to a stream in which the CO₂ content islower than that of the CO₂ content in the CO₂ stream 101. In someembodiments, as noted earlier, almost all of the CO₂ in the CO₂ streamis condensed in the step 13. In such embodiments, the lean CO₂ stream issubstantially free of CO₂. In some other embodiments, as noted earlier,a portion of the CO₂ stream may not condense in the step 13 and the leanstream may include uncondensed CO₂ gas mixture.

In some embodiments, the lean stream 202 may include one or morenon-condensable components, which may not condense in the step 13. Insome embodiments, the lean stream 202 may include one or more liquidcomponents. In such embodiments, the lean stream may be furtherconfigured to be in fluid communication with a liquid-gas separator. Insome embodiments, the lean stream 202 may include one or more ofnitrogen, oxygen, or sulfur dioxide.

In some embodiments, the method may further include dehumidifying theCO₂ stream 101 before step 11. In some embodiments, the method mayfurther include dehumidifying the partially cooled CO₂ stream 201 afterstep 11 and before step 12. In some embodiments, the system 100 mayfurther include a dehumidifier configured to be in flow communication(not shown) with the CO₂ stream 101. In some embodiments, the system 100may further include a dehumidifier configured to be in flowcommunication (not shown) with the CO₂ stream 101.

In some embodiments, the method further includes circulating thecondensed CO₂ stream 302 to one or more cooling stages used for coolingthe CO₂ stream. As indicated in FIG. 5, the method further includescirculating the condensed CO₂ stream to a heat exchanger 113 via acirculation loop 303. In such embodiments, the method further includes arecuperation step where the condensed CO₂ stream is circulated back tofurther cool the partially cooled CO₂ stream 201 before themagneto-caloric cooling step 12. In some embodiments, the recuperationstep may increase the efficiency of the magneto-caloric step.

In some embodiments, the recuperation of condensed CO₂ stream to theheat exchanger 113 may result in cooling of the partially cooled CO₂stream 201 below the temperature required for condensation of CO₂. Insome embodiments, the method may further include condensing the CO₂ inthe partially cooled CO₂ stream 201 to form a recuperated condensed CO₂stream 501, as indicated in FIG. 5.

In some embodiments, the method further includes increasing a pressureof the condensed CO₂ stream 302 using a pump 300, as indicated in FIG.3. In embodiments including a recuperation step, the method may furtherinclude increasing a pressure of the recuperated condensed CO₂ stream501 using a pump 300, as indicated in FIG. 5. In some embodiments, themethod includes increasing a pressure of the condensed CO₂ stream 302 orthe recuperated condensed CO₂ stream 502 to a pressure desired for CO₂sequestration or end-use. In some embodiments, the method includesincreasing a pressure of the condensed CO₂ stream 302 or the recuperatedcondensed CO₂ stream 502 to a pressure in a range from about 150 bar toabout 180 bar.

In some embodiments, the method further includes generating apressurized CO₂ stream 401 after the pumping step. In some embodiments,the method further includes generating a supercritical CO₂ stream 401after the pumping step. In some embodiments, as noted earlier, thepressurized CO₂ stream 401 may be used for enhanced oil recovery, CO₂storage, or CO₂ sequestration.

In some embodiments, a system 100 for condensing carbon dioxide (CO₂)from a CO₂ stream 101 is provided, as illustrated in FIGS. 3-9. In oneembodiment, the system 100 includes one or more compression stages 120configured to receive the CO₂ stream 101. The system 100 furtherincludes one or more cooling stages 110 in fluid communication with theone or more compression stages 120. In one embodiment, a combination ofthe one or more compression stages 120 and the one or more coolingstages 110 is configured to compress and cool the CO₂ stream 101 to afirst temperature to form a partially-cooled CO₂ stream 201.

In one embodiment, the system 100 further includes a magneto-caloriccooling stage 200 configured to receive the partially-cooled CO₂ stream201 and cool the partially-cooled CO₂ stream 201 to a second temperatureto form a cooled CO₂ stream 301. As noted earlier, the magneto-caloriccooling stage 200 further includes a heat exchanger 212, wherein themagneto-caloric cooling device 211 is configured to provide cooling tothe heat exchanger 212. In one embodiment, the heat exchanger 212 is influid communication with the one or more cooling stages 110 and the oneor more compression stages 120.

As noted earlier, in some embodiments, the heat exchanger 212 isconfigured to condense a portion of CO₂ in the partially cooled CO₂stream 201 to form the condensed CO₂ stream 302. In some otherembodiments, the system 100 further includes a condensation stage 213configured to condense a portion of CO₂ in the cooled CO₂ stream 301 atthe second temperature, thereby condensing CO₂ from the cooled CO₂stream 301 to form a condensed CO₂ stream 302.

In some embodiments, the system 100 further includes a pump 300configured to receive the condensed CO₂ stream 302 and increase thepressure of the condensed CO₂ stream 302. In some embodiments, thesystem further includes a circulation loop 303 configured to circulate aportion of the condensed CO₂ stream 302 to the one or more coolingstages 110.

With the foregoing in mind, systems and methods for condensing CO₂ froma CO₂ stream, according to some exemplary embodiments of the invention,are further described herein. Turning now to FIGS. 2 and 3, in oneembodiment, a method 20 of condensing carbon dioxide from a CO₂ stream101 is provided. In one embodiment, the method includes, at step 21,cooling the CO₂ stream 101 in a first cooling stage including a firstheat exchanger 111 to form a first partially cooled CO₂ stream 102. Inone embodiment, the method includes, at step 22, compressing the firstpartially cooled CO₂ stream 102 in a first compressor 121 to form afirst compressed CO₂ stream 103. In one embodiment, the method includes,at step 23, cooling the first compressed CO₂ stream 103 in a secondcooling stage including a second heat exchanger 112 to form a secondpartially cooled CO₂ stream 104. In one embodiment, the method includes,at step 24, compressing the second partially cooled CO₂ stream 104 in asecond compressor 122 to form a second compressed CO₂ stream 105. In oneembodiment, the method includes, at step 25, cooling the secondcompressed CO₂ stream 105 to a first temperature in a third coolingstage comprising a third heat exchanger 113 to form a partially cooledCO₂ stream 201.

In one embodiment, the method 20 includes, at step 26, cooling thepartially cooled CO₂ stream 201 to a second temperature bymagneto-caloric cooling using a magneto-caloric cooling stage 200 toform a cooled CO₂ stream (not shown). In some embodiments, amagneto-caloric cooling stage 200 includes a heat exchanger 212 and anexternal magneto-caloric cooling device 211. In some embodiments, themagneto-caloric cooling device 211 is configured to provide cooling tothe heat exchanger 212, as indicated in FIG. 3.

In one embodiment, the method includes, at step 27, condensing at leasta portion of CO₂ in the cooled CO₂ stream at the second temperature,thereby condensing CO₂ from the cooled CO₂ stream to form a condensedCO₂ stream 302. As noted earlier, in some embodiments, a cooled CO₂stream is generated from the partially cooled CO₂ stream 201 in the heatexchanger 212. In such embodiments, a portion of CO₂ from the cooled CO₂stream condenses in the heat-generator itself forming a condensed CO₂stream 302, as indicated in FIG. 3.

In some embodiments, the method further includes increasing a pressureof the condensed CO₂ stream 302 using a pump 300, as indicated in FIG.3. In some embodiments, the method further includes generating apressurized CO₂ stream 401 after the pumping step. In some embodiments,as noted earlier, the pressurized CO₂ stream 401 may be used forenhanced oil recovery, CO₂ storage, or CO₂ sequestration.

Turning now to FIG. 4, in one embodiment, a method and a system forcondensing CO₂ from a CO₂ stream 101 is provided. The method and systemis similar to the system and method illustrated in FIG. 3, with theaddition that the method further includes transferring the cooled CO₂stream 301 to a condenser 213, as indicated in FIG. 4. In suchembodiments, a portion of CO₂ from the cooled CO₂ stream 301 condensesin the condenser 213 and forms a condensed CO₂ stream 302, as indicatedin FIG. 4.

Turning now to FIG. 5, in one embodiment, a method and a system forcondensing CO₂ from a CO₂ stream 101 is provided. The method and systemis similar to the system and method illustrated in FIG. 3, with theaddition that the method further includes circulating a portion of thecondensed CO₂ stream 302 to the third heat exchanger 113 via acirculation loop 303. As noted earlier, in some embodiments, therecuperation of condensed CO₂ stream to the heat exchanger 113 mayresult in cooling of the second compressed CO₂ stream 105 below thetemperature required for condensation of CO₂. In some embodiments, themethod may further include condensing the CO₂ in the second compressedCO₂ stream 105 to form a recuperated condensed CO₂ stream 501, asindicated in FIG. 5.

Turning now to FIG. 6, in one embodiment, a method and system forcondensing CO₂ from a CO₂ stream 101 is provided. The method and systemis similar to the system and method illustrated in FIG. 4, with theaddition that the method further includes circulating a portion of thecondensed CO₂ stream to the third heat exchanger 113 via a circulationloop 303. As noted earlier, in some embodiments, the recuperation ofcondensed CO₂ to the heat exchanger 113 may result in cooling of thesecond compressed CO₂ stream 105 below the temperature required forcondensation of CO₂. In some embodiments, the method may further includecondensing the CO₂ in the second compressed CO₂ stream 105 to form arecuperated condensed CO₂ stream 501, as indicated in FIG. 6.

Turning now to FIG. 7, in one embodiment, a method and a system forcondensing CO₂ from a CO₂ stream 101 is provided. The method and systemis similar to the system and method illustrated in FIG. 3, with theaddition that the method further includes circulating a portion of thepressurized CO₂ stream 401 to the third heat exchanger 113 via acirculation loop 403. As noted earlier, in some embodiments, therecuperation of pressurized CO₂ stream 401 to the third heat exchanger113 may result in cooling of the second compressed CO₂ stream 105 belowthe temperature required for condensation of CO₂. In some embodiments,the method may further include condensing the CO₂ in the secondcompressed CO₂ stream 105 to form a recuperated condensed CO₂ stream501, as indicated in FIG. 7.

Turning now to FIG. 8, in one embodiment, a method and a system forcondensing CO₂ from a CO₂ stream 101 is illustrated. The method andsystem is similar to the system and method illustrated in FIG. 3, withthe addition that the method further includes forming a third partiallycooled CO₂ stream 106 in the third heat exchanger 113. The methodfurther includes cooling the third partially cooled CO₂ stream 106 to afirst temperature by expanding the third partially cooled CO₂ stream 106in one or more expanders 123, before the magneto-caloric cooling step,to form the partially-cooled CO₂ stream 201, as indicated in FIG. 8.

Turning now to FIG. 9, in one embodiment, a method and a system forcondensing CO₂ from a CO₂ stream 101 is illustrated. The method andsystem is similar to the system and method illustrated in FIG. 8, withthe addition that the third cooling stage further comprises a fourthheat exchanger 114, and the method further includes circulating aportion of the pressurized CO₂ stream 401 to the fourth heat exchanger114 via a circulation loop 403. The method further includes forming afourth partially cooled CO₂ stream 107 after the expansion step andtransferring the fourth partially cooled CO₂ stream 107 to the fourthheat exchanger 114. As noted earlier, in some embodiments, therecuperation of pressurized CO₂ stream 401 to the fourth heat exchanger114 may result in cooling of the fourth partially cooled CO₂ stream 107below the temperature required for condensation of CO₂. In someembodiments, the method may further include condensing the CO₂ in thefourth partially cooled CO₂ stream 107 to form a recuperated condensedCO₂ stream 501, as indicated in FIG. 9.

As noted earlier, some embodiments of the invention advantageously allowfor cooling of the supercritical CO₂ to lower temperatures andsubsequent condensation at lower pressures than those available throughconventional cooling methods, such as, vapor compression. Without beingbound by any theory, it is believed that compression of supercriticalCO₂ may be less efficient than pumping liquid CO₂. Thus, in someembodiments, the method reduces the penalty on the less-efficient CO₂compression step. In some embodiments, the method may reduce the overallpenalty for CO₂ liquefaction and pumping by improving the efficiency ofthe compression and pumping system. In some embodiments, themagneto-caloric cooling stage may reduce the penalty by more than 10%.In some embodiments, the magneto-caloric cooling stage may reduce thepenalty by more than 20%. In some embodiments, the overall plantefficiency may be improved by using one or more of the methodembodiments, described herein.

Further, some embodiments of the invention advantageously allow forimproved range of operability of CO₂ compression and liquefactionsystems. In conventional CO₂ compression and liquefaction systems, theambient temperature of the cooling air or cooling water may limit therange of operability. Supercritical CO₂ may not liquefy at temperaturesgreater than about 32° C., the critical temperature of CO₂. Thus, whenambient temperatures are above 30° C., liquefaction of CO₂ may bedifficult without additional external cooling. In some embodiments, themagnetic cooling step may advantageously allow cooling of CO₂ to thesubcritical range, thereby enabling the operability of the compressionand liquefaction systems under any ambient conditions.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

What is claimed is:
 1. A method of condensing carbon dioxide (CO₂) froma CO₂ stream, comprising: (i) compressing and cooling the CO₂ stream toform a partially cooled CO₂ stream, wherein the partially cooled CO₂stream is cooled to a first temperature; (ii) cooling the partiallycooled CO₂ stream to a second temperature by magneto-caloric cooling toform a cooled CO₂ stream; and (iii) condensing at least a portion of CO₂in the cooled CO₂ stream to form a condensed CO₂ stream.
 2. The methodof claim 1, wherein step (iii) comprises condensing at least a portionof CO₂ in the cooled CO₂ stream at a pressure in a range of from about20 bar to about 60 bar.
 3. The method of claim 1, wherein step (iii)comprises condensing at least a portion of CO₂ in the cooled CO₂ streamat a pressure in a range of from about 20 bar to about 40 bar.
 4. Themethod of claim 1, wherein the first temperature is in a range of fromabout 5 degrees Celsius to about 35 degrees Celsius
 5. The method ofclaim 1, wherein the second temperature is in a range of from about 0degrees Celsius to about −25 degrees Celsius
 6. The method of claim 1,wherein step (i) comprises cooling the CO₂ stream using one or morecooling stages comprising one or more heat exchangers.
 7. The method ofclaim 1, further comprising circulating a portion of the condensed CO₂stream to one or more cooling stages used for cooling the CO₂ stream. 8.The method of claim 1, wherein step (i) comprises cooling the CO₂ streamto the first temperature by expanding the CO₂ stream in one or moreexpanders.
 9. The method of claim 1, wherein step (ii) comprises coolingthe partially-cooled CO₂ stream using a rotary magneto-caloric coolingdevice.
 10. The method of claim 1, further comprising increasing apressure of the condensed CO₂ stream using a pump to form a pressurizedCO₂ stream.
 11. A method of condensing carbon dioxide (CO₂) from a CO₂stream, comprising: (i) cooling the CO₂ stream in a first cooling stagecomprising a first heat exchanger to form a first partially cooled CO₂stream; (ii) compressing the first partially cooled CO₂ stream to form afirst compressed CO₂ stream; (iii) cooling the first compressed CO₂stream in a second cooling stage comprising a second heat exchanger toform a second partially cooled CO₂ stream; (iv) compressing the secondpartially cooled CO₂ stream to form a second compressed CO₂ stream; (v)cooling the second compressed CO₂ stream to a first temperature in athird cooling stage comprising a third heat exchanger to form apartially cooled CO₂ stream; (vi) cooling the partially cooled CO₂stream to a second temperature by magneto-caloric cooling to form acooled CO₂ stream; and (vii) condensing at least a portion of CO₂ in thecooled CO₂ stream at the second temperature, thereby condensing CO₂ fromthe cooled CO₂ stream to form a condensed CO₂ stream.
 12. The method ofclaim 11, further comprising circulating a portion of the condensed CO₂stream to the third heat exchanger.
 13. The method of claim 11, whereinthe third cooling stage further comprises an expander, and step (v)further comprises cooling the CO₂ stream to a first temperature byexpanding the second compressed CO₂ stream in the expander.
 14. Themethod of claim 13, wherein the third cooling stage further comprises afourth heat exchanger, and the method further comprises circulating aportion of the condensed CO₂ stream to the fourth heat exchanger.
 15. Asystem for condensing carbon dioxide (CO₂) from a CO₂ stream,comprising: (i) one or more compression stages configured to receive theCO₂ stream; (ii) one or more cooling stages in fluid communication withthe one or more compression stages, wherein a combination of the one ormore compression stages and the one or more cooling stages is configuredto compress and cool the CO₂ stream to a first temperature to form apartially-cooled CO₂ stream; (iii) a magento-caloric cooling stageconfigured to receive the partially-cooled CO₂ stream and cool thepartially-cooled CO₂ stream to a second temperature to form a cooled CO₂stream; and (iv) a condensation stage configured to condense a portionof CO₂ in the cooled CO₂ stream at the second temperature, therebycondensing CO₂ from the cooled CO₂ stream to form a condensed CO₂stream.
 16. The system of claim 15, wherein the magneto-caloric coolingstage comprises a magneto-caloric cooling device and a heat exchanger,wherein the heat exchanger is in fluid communication with the one ormore cooling stages and the one or more compression stages.
 17. Thesystem of claim 15, further comprising a pump configured to receive thecondensed CO₂ stream and increase the pressure of the condensed CO₂stream.
 18. The system of claim 15, wherein the one or more coolingstages further comprises an expander.
 19. The system of claim 15,wherein the one or more cooling stages comprises one or more heatexchangers configured to cool the CO₂ stream using air, water, orcombinations thereof.
 20. The system of claim 15, further comprising acirculation loop configured to circulate a portion of the condensed CO₂stream to the one or more cooling stages.